The mesentery is a double fold of peritoneal tissue that suspends the small intestine and large intestine from the posterior abdominal wall.

It was previously thought to be a collection of discrete structures – each with separate insertions into the posterior wall. However, recent research has found the mesentery to be one contiguous structure, which has led to proposals for its reclassification as an organ.

In this article, we shall look at the anatomy of the mesentery – its anatomical structure, vasculature, innervation, lymphatics and clinical relevance.

Note: Research regarding the mesentery is relatively recent, and some older textbooks may still describe the different parts of the mesentery as separate structures – this is now thought to be incorrect.

Structure

Although the mesentery is now thought to be a contiguous structure, subsections of the mesentery can be named according to the viscera it is associated with. Thus, names such as mesocolon, mesorectum, mesosigmoid all relate to different parts of the mesentery.

The ‘root’ of the mesentery is the point where the mesentery attaches to the posterior abdominal wall, and is therefore a ‘bare area’. Due to the range of abdominal organs the mesentery envelopes, the root is long, narrow and has an oblique orientation, from the left side of the L2 vertebra to the right sacroiliac junction roughly.

In the gastrointestinal tract, there are six flexures of note: duodenojejunal, ileocaecal, hepatic, splenic, and those between the descending and sigmoid colon and the sigmoid and rectum. These flexures are often used to mark the distinction between different portions of the mesentery:

Mesentery of the small intestine – connects the loops of jejunum and ileum to the posterior abdominal wall and is a mobile structure. (1)

Right mesocolon – flattened against the posterior abdominal wall (2)

Transverse mesocolon – a mobile structure and lies between the colic flexures (3)

Left mesocolon – flattened against the posterior abdominal wall (4)

Mesosigmoid – has a medial portion which is flattened against the posterior abdominal wall, whereas the region of mesentery associated with the sigmoid colon itself is mobile. (5)

Fig 2 – Small intestine and and large intestine highlighted to show associated mesentery.

The areas of the mesentery that are flattened against the posterior abdominal wall (the right and left mesocolon and the medial mesosigmoid) are attached to the abdominal wall via an additional layer of connective tissue known as Toldt’s fascia. The fascia contains several lymphatic channels.

Clinical Relevance: Intestinal Volvulus

A volvulus occurs when a loop of intestine twists around itself and its mesentery, causing obstruction of the bowel. It is possible that the bowel will twist tightly enough to prevent the blood supply to the intestine, and result in bowel infarction.

The most commonly affected area of bowel is the sigmoid colon. The risk of intestinal volvulus is increased in children with intestinal malrotation, a congenital defect in which the embryological intestinal rotation is incomplete, resulting in improper anchoring of the intestines to the posterior abdominal wall.

Vasculature

The mesentery acts a conduit for neurovascular structures.

The superior and inferior mesenteric arteries (SMA and IMA) arise from the abdominal aorta and travel in the mesentery to supply the abdominal viscera. These vessels also give rise to branches that supply the mesentery itself.

Superior mesenteric artery – supplies the organs of the midgut – from the major duodenal papilla to the proximal two thirds of the transverse colon.

Inferior mesenteric artery – supplies the organs of the hindgut – the distal one third of the transverse colon, splenic flexure, descending colon, sigmoid colon and rectum.

Fig 5 – Major branches of the inferior mesenteric artery demonstrated in green

Innervation

The superior mesenteric plexus (a continuation of the celiac plexus) accompanies the superior mesenteric artery into the mesentery.

The superior mesenteric plexus then divides into many secondary plexuses which contain parasympathetic and sympathetic innervation to the mesentery associated with a particular organ, the organs themselves and their related blood vessels.

Lymphatics

The mesentery contains both lymph nodes and lymphatic vessels. There are several groups of lymph nodes found within the mesentery:

Results

Recommended for You

You need to be a gold member supporter to access this content. Please support us here or upgrade in your account.

The medical information on this site is provided as an information resource only, and is not to be used or relied on for any diagnostic or treatment purposes. This information is intended for medical education, and does not create any doctor-patient relationship, and should not be used as a substitute for professional diagnosis and treatment.

By visiting this site you agree to the foregoing terms and conditions. If you do not agree to the foregoing terms and conditions, you should not enter this site.